The present invention relates to corrosion prevention associated with field of intergranular corrosion (IGC) and/or intergranular stress corrosion cracking (IGSCC) resistance. Intergranular corrosion is a special form of corrosion characterized by the preferential attack of the grain boundaries. Intergranular corrosion (IGC) is also referred to as intergranular attack (IGA). IGC corrosion only occurs if the grain boundary regions are compositionally different from the bulk of the alloy. This compositional difference occurs during usage of the structure exposed to with time, or heat treating, aging, or welding by diffusion of atoms and precipitation of second phase particles. In 5000 series Al—Mg alloys with high Mg content (>3% Mg) solid solution is supersaturated with Mg solute atoms, because the Mg content is higher than 1.9% Mg, which is the equilibrium solubility of Mg in Al-matrix at room temperature. In that case, Mg solute atoms tend to precipitate out as an equilibrium β-phase (Mg5Al8) along the grain boundaries or randomly distributed in the structure during usage of the structure exposed to with time, or heat treating, aging, or welding by diffusion of atoms and precipitation of second phase particles. Precipitation sequences of the decomposition of supersaturated solid solution have been reported earlier as follows:                α-Al matrix→GP zones→(β′-phase→(β-phase (Mg5Al8)This process occurs slowly even at room temperature, and could be significantly accelerated at high temperatures (>65° C.). Since the corrosion potential of β-phase (−1.24V), is more negative than the potential of Al-matrix (−0.87V), dissolution of anodic (β-phase particles would occur in an appropriate solution, such as seawater. Corrosion, particularly in highly corrosive environments, is a substantial maintenance problem. A desirable aspect of manufacturing of equipment is to prevent corrosion rather than take corrective actions after corrosion has occurred. Classic responses to corrosion include chipping, scraping, painting and washing structures on a continual basis. However, up front prevention leverages downstream savings.        
According to one illustrative embodiment of the present disclosure, an exemplary process includes a method, structure, and/or material composition associated with overetching a structure or allow of interest to create a depletion zone or deplete magnesium content at and in a vicinity of grain boundaries which mitigates or prevents corrosion including, for example, IGC and/or IGSCC. Another aspect of the invention can include a process, structure and/or a material composition associated with providing a particular coating, e.g., a ceramic coating of various alloy parts, e.g., aluminum parts such as discussed herein. Additional steps, material composition(s), and/or exemplary structure can also be provided which provides a nano coating over a depletion zone having a first coating in accordance with an embodiment of the invention.
Additional features and advantages of the present invention will become apparent to those skilled in the art upon consideration of the following detailed description of the illustrative embodiment exemplifying the best mode of carrying out the invention as presently perceived.